TUBE OPERATION 2
Fig 5. Graph of 6SN7 Ra curves with load lines for 47k and 32k.
How to find Ra for a given working point and plot loadlines in
steps
1 to19.
Comment on THD and other topology outcomes.
Fig 6. Scanned Ra curves from Samuel Seely, 1958.
Explanations about the Ra curves. About gain with CCS load and
µ.
6SN7 THD with CCS load calculations from data curves.

TUBE OPERATION 3
How negative feedback works.
Fig 7. Schematic for Basic NFB around an amplifier.
Explanations and formula for NFB gain reductions and effects of
NFB.
Fig 8. Schematic for TA 35Watt class AB triode amp
using KT90.
General notes about this amp which has the same overall gain and
NFB
as the basic example in Fig1.
Calculation method for output resistance with NFB.
The Model of the tube gain stage as a voltage generator.
Fig 9. Schematic of a power tube gain stage modeled as a
generator
with resistor to indicate Ra.
Explanations about the generator model.
Fig 10. Schematic of a tube gain stage using 6SN7.
Fig 11. Schematic of a tube amp drawn with each stage as a generator
with loads and positions of shunt C to analyze the HF response and
graph all the attenuation profiles.
A whole lot more about NFB, output resistance.
A simple formula for calculating output resistance of a real
amp.
More on stability of amplifiers with NFB and the use of RC
networks
to tailor open loop gain.
Fig 12. Graph of tube amp frequency response without global NFB
and
with global NFB, with no attempts to tailor open loop gain or
phase shift.
Fig 13. Graph of tube amp frequency response without and with
NFB
but with RC gain and phase shift tailoring
networks in place.
More about stability and NFB.
Critical damping methods for tube amps with NFB.

TUBE OPERATION 5
About Input and Driver stages for PP tube amps.
Fig1. Schematic for basic input LTP.
Fig 2. Schematic for Driver LTP with balanced or un-balanced
inputs.
Fig 3. Schematic for Optimal LTP input and driver LTP for high
level operation.
All explained with many calculations and considerations.

----------------------------------------------------------------------------------------SE AMP OUTPUT STAGE
CONFIGURATIONSContent of this page is based
around schematics.Fig 1. Three most used basic SE amp stages,
13W to 10W, SE pure
tetrode, SE Ultralinear, SE triode, 1 x KT88/6550.Fig 2. 20W+ amp with SEUL with 2 x EL34, KT66,
KT88, KT90, KT120. Fig 3. The Equivalent Model of KT88 with g1
and g2 inputs treated as
current generators.
This allows understanding of
operating properties of a KT88, and its
Ra, gm g1, gm g2, and to analyze all voltages and currents in all
electrodes to
determine voltage gain, and effect of local NFB.
The theory may be applied to all
power tubes including pure triodes
which do not have a screen, such as
300B and 2A3. Fig 4. 20W+ amp with CFB, with 2 x EL34, KT66,
KT88, KT90, KT120,
using same SEUL OPT in Fig 2.Fig 5. 36W SE amp with CFB with 3 x KT88 etc,
using SEUL OPT,
25% UL tap, 1k3 : 5r6 Z ratio.
This was designed to include
"choke sink" for cathode current, and
choke in anode feed for driver tube.
Probably nobody has
ever built an amp like this because they need
to source good quality chokes.
The THD and Rout is much lower than conventional SEUL amps.Fig 6. 25W PSEUL + CFB
amp designed around the Hammond
1640SEA output transformer with mosfet CCS at KT88 cathodes,Fig 7.25W PSEUL + CFB amp designed
around the
Hammond
1640SEA output transformer with choke at KT88 cathodes,Fig
8. SE CFB output stage and SEUL output stages with
OPT
with 3 windings.Fig 9. Choke Feed SEUL
and SET output stages.Fig 10. Choke Feed SET
amp with 845.Fig 11. Choke Feed
SEUL with floating B+ supply.Fig 12. Choke Feed SET
with floating B+ supply.

----------------------------------------------------------------------------ANODE DISSIPATION
Page 2
This page still being written 2015...
Calculations of tube or solid-state device heat dissipation for
class
AB or B amps with low bias currents, and without OPTs, aka "OTL"
amps with 6C33C or 6AS7G. Graphs and calculation examples, etc.
The subject is covered in OTL
AMPS, PROS AND CONS.
------------------------------------------------------------------------------SINGLE ENDED OUTPUT TRANSFORMER
CALCULATIONS.3 pages for this subject.

AM GENERATION WITH SOLID STATEPrinciples of AM generation using bjts and mosfets,
many schematics and wave forms,
and why I chose not to use solid state to make an RF signal gene with AM
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RF GENERATION WITH TUBES AND AM AND FM
RF gene for workshop for 375kHz to 1,750kHz in two tunable bands.
The RF can be amplitude modulated with AF between 5Hz and 20kHz.
3 selectable RF bands are FM modulated using zener diodes as varicaps
with internal 30Hz saw toot ramp generator.
Sheets 1, 2, 3 for all signal circuits. You need to be able to make your own
PSU to give the +/- Vdc rails shown. This complex unit is not for beginners.
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